Abstract Solar flare gamma-ray emissions from energetic ions and electrons have been detected and measured to GeV energies since 1980. In addition, neutrons produced in solar flares with 100MeV to GeV energies have been observed at the Earth. These emissions are produced by the highest energy ions and electrons accelerated at the Sun and they provide our only direct (albeit secondary) knowledge about the properties of the accelerator(s) acting in a solar flare. The solar flares, which have direct evidence for pion-decay gamma-rays, are unique and are the focus of this paper. We review our current knowledge of the highest energy solar emissions, and how the characteristics of the acceleration process are deduced from the observations. Results from the RHESSI, INTEGRAL and CORONAS missions will also be covered. The review will also cover the solar flare capabilities of the new mission, FERMI GAMMA RAY SPACE TELESCOPE, launched on 2008 June 11. Finally, we discuss the requirements for future missions to advance this vital area of solar flare physics.
Keywords Sun— Flares— Particle Acceleration-Meson Production
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